emtalk nearfield
I need to evaluate the scattering matrix of a patch antenna to design a reflectarray. The evaluation of the scattering matrix is, usually, obtained by considering a periodic structure under different angle of incidence, by using a plane wave illumination.
I've considered a single patch cell (see attached file), and i have used the master slave boundary condition to get a periodic structure. I used a phase term on the slave boundary according to the plane wave incidence direction (th,phi):
i.e. (slave boundary orthogonal to the x axis) --> (a/lambda)*sin(th)*cos(ph)
(slave boundary orthogonal to the x axis) --> (b/lambda)*sin(th)*sin(ph)
where a and b are the cell dimensions.
Unfortunately i did non get what i expected!
In fact, the maximum of the total reflected field is not exactly in the specular direction: in the attached case i considered th=30degree phi=20degree, and i get the maximum along the direction th=-25degree end phi=15degree.
I tried to improve the mesh and the setup, and i also tried to use the spherical setup for the plane wave, instead of the definition in cartesian system. moreover i also tired PML instead of RAD condition.
I guess the problem is in the Master Slave phase term.
CAN ANYONE HELP ME?!?!
Thanks clod
BUG IN THE PLANE WAVE DEFINITION under the cartesian system.
if i set the propagation vector component as the usual u,v and w definition, by using th and phi as parameter, and the E vector written as the th versor, ONLY for certain angle couples i get a message of non orthogonality between K and E.
Further info....
if i refer to a metallic plate (i.e. i remove the substrate and the patch leaving only the ground plane), and i remove the periodic Master Slave condition, i get the maximum field intensity in the specular direction (exactly!).
All with no changes in the mesh and analysis setup.
This is the reason i think i do not use in the exact way the master slave boundary
Many Thanks
there is tutorial on master/slave boundary at
http://www.emtalk.com/tut_2.htm
and
http://www.emtalk.com/tut_3.htm
hi savedadogs!
thank you! but it does not refer to the far field evaluation...
Other suggestions[/quote]
I got some news about the problem.
I found a tutorial where the bistatic RCS if calculated.
It does not evaluate directly the radiated far field, but the field used in the RCS is obtained by evaluating the power flow across a proper surface located in the near field zone.
I attached the file.
Someone is interested in or have already used such approach?!?
Thankx
C
in cst2008,new version,an easy way to see ur phase variation using floquet modes,there is an example,u could get it from the tutorials of cst
regards